The alarmone ppGpp is an important signal molecule for the stringent response. Escherichia coli relA encodes a ppGpp synthetase, and although the regulation of RelA protein activity has been studied extensively, the regulation of relA transcription remains unclear. Here, we describe a novel relA promoter, relAP2. According to quantitative measurement of mRNA by primer extension analysis, the previously reported promoter relAP1 is constitutively active throughout growth, while relAP2 is induced temporarily at the transition state between the exponential growth and stationary phases. A chromosomal transcriptional lacZ fusion (relAP2-lacZ) showed that relAP2 is positively regulated by H-NS and CRP. Furthermore, the reduced activity of relAP2-lacZ in an hns mutant could be rescued by an rpoS mutation, which is sufficient to derepress the relAP2-lacZ activity. These data suggest that transient expression from the relAP2 promoter is controlled by several global regulators. This may account for the complex regulation of relA expression in Escherichia coli.
Recently, the complete chloroplast genome sequences of many important crop plants were determined, and this can be considered a major step forward toward exploiting the usefulness of chloroplast genetic engineering technology. Economically, cotton is one of the most important crop plants for many countries. To further our understanding of this important crop, we determined the complete nucleotide sequence of the chloroplast genome from cotton (Gossypium barbadense L.). The chloroplast genome of cotton is 160,317 base pairs (bp) in length, and is composed of a large single copy (LSC) of 88,841 bp, a small single copy (SSC) of 20,294 bp, and two identical inverted repeat (IR) regions of 25,591 bp each. The genome contains 114 unique genes, of which 17 genes are duplicated in the IRs. In addition, many open reading frames (ORFs) and hypothetical chloroplast reading frames (ycfs) with unknown functions were deduced. Compared to the chloroplast genomes from 8 other dicot plants, the cotton chloroplast genome showed a high degree of similarity of the overall structure, gene organization, and gene content. Furthermore, the sequences of the genes showed high degrees of identity at the DNA and amino acid levels. The cotton chloroplast genome was somewhat longer than the chloroplast genomes of most of the other dicot plants compared here. However, this elongation of the cotton chloroplast genome was found to be due mainly to expansions of the intergenic regions and introns (non-coding DNA). Moreover, these expansions occurred predominantly in the LSC and SSC regions.
Fagopyrum urophyllum is a cross-pollinating perennial woody shrub species belonging to the urophyllum group of Fagopyrum. Natural populations of F. urophyllum were morphologically classified into two distinct groups, the Dali group and the Kunming group without exception. This grouping was verified by molecular phylogeny based on the nucleotide sequence of chloroplast DNA. The reproductive isolation found between the two groups was almost perfect as the distribution of two groups did not overlap each other. The net nucleotide substitution rate (Da) between the two groups was at the same level as between two distinct species. These data suggests that the two groups should be classified into distinct species if future studies on F. urophyllum confirm complete reproductive isolation and no ambiguously classified populations in the border area of the central Yunnan province of China.
The MCJ gene is a member of the DNAJ family, and its transcriptional event is controlled by methylation of the CpG island. In our study, we found LTR33 and LTR7 elements provided an alternative transcript within the MCJ gene. To detect different expression patterns between the originally reported MCJ transcript and the LTR-related transcript, we performed a RT-PCR approach using various human tissues and cancer cells. The original MCJ transcript was detected in human tissues and cancer cells, whereas the LTR-related transcript was only revealed in some cancer cells (HCT106, MCF-3, TE-1, Hela, and CCHM). We also performed a PCR analysis to compare the insertion lineage of the LTR elements with the genomic DNAs of primates, indicating that those LTR33 and LTR7 elements of HERV-H have been integrated into the primate genome at different times. Taken together, we suggest that HERV-related elements trigger transcriptome diversification during primate evolution.
In Drosophilamelanogaster, the Sir2 gene and four Sir2-like genes have been found to be homologous to yeast SIR2 genes. To examine whether the fly Sir2, CG5216, and two Sir2-like genes, CG5085 and CG6284, affect life span, we suppressed their expression using RNAi. Decreased expression of the Sir2 and Sir2-like genes in all cells caused lethality during development. Suppression of the Sir2 in neurons and ubiquitous silencing of the Sir2-like genes shortened life spans. The effects were severer at 28°C than at 25°C. These results suggest that Sir2-like genes as well as Sir2 are involved in the regulation of life span in Drosophila.
Under low temperature conditions, the cytochrome pathway of respiration is repressed and reactive oxygen species (ROS) are produced in plants. Mitochondrial alternative oxidase (AOX) is the terminal oxidase responsible for the cyanide-insensitive and salicylhydroxamic acid-sensitive respiration. To study functions of wheat AOX genes under low temperature, we produced transgenic Arabidopsis by introducing Waox1a expressed under control of the cauliflower mosaic virus (CaMV) 35S promoter in Arabidopsis thaliana. The enhancement of endogenous AOX1a expression via low temperature stress was delayed in the transgenic Arabidopsis. Recovery of the total respiration activity under low temperature occurred more rapidly in the transgenic plants than in the wild-type plants due to a constitutively increased alternative pathway capacity. Levels of ROS decreased in the transgenic plants under low temperature stress. These results support the hypothesis that AOX alleviates oxidative stress when the cytochrome pathway of respiration is inhibited under abiotic stress conditions.
RRM (RNA-recognition motif) domain is important for the post-transcriptional regulation of gene expression including RNA processing. In our previous study, we found one anther- and/or pollen-specific gene (LjRRM1, previously named as LjMfb-U93) in model legume, Lotusjaponicus. Because of the richness of genomic information of another model plant, Arabidopsisthaliana, for functional analysis, we identified and characterized the orthologous genes in A. thaliana. By comparison of the partial nucleotide sequence of LjRRM1 to the public database, we identified three homologous genes (AtRBP45a, AtRBP45b, and AtRBP45c) in A. thaliana genome. Based on promoter analysis, both AtRBP45a and AtRBP45c were specifically expressed in immature anther tissues (tapetum cells) and mature pollen grains of transgenic plants. This expression pattern of AtRBP45a and AtRBP45c is quite similar to that of LjRRM1, indicating that AtRBP45a and AtRBP45c would be orthologous to LjRRM1. Because in another previous experiment, it was shown that proteins having RRM domains were related to pre-mRNA maturation, and as a conclusion, it is possible that LjRRM1, AtRBP45a, and AtRBP45c genes encoding RNA-binding proteins are functionally involved in the repression of translation in mature pollen grains in L. japonicus and A. thaliana.
The major components of storage starch are amylose and amylopectin, and in wheat, both an amylose-free mutant lacking granule-bound starch synthase I and a high-amylose mutant lacking starch synthase IIa have been produced recently. Here, we report the production of an amylose-free/ high-amylose double mutant. This double mutant has kernel and carbohydrate characteristics that are remarkably different than those of either single mutant, including a dramatically shrunken seed shape. Surprisingly, the double mutant has maltose and sucrose levels that are high enough to make it worthy of being called “sweet wheat”.
The globin family of genes and proteins has been a recurrent object of study for many decades. This interest has generated a vast amount of knowledge. However it has also created an inconsistent and confusing nomenclature, due to the lack of a systematic approach to naming genes and failure to reflect the phylogenetic relationships among genes of the gene family. To alleviate the problems with the existing system, here we propose a standardized nomenclature for the α and β globin family of genes, based on a phylogenetic analysis of vertebrate α and β globins, and following the Guidelines for Human Gene Nomenclature.